kotlin1.3 multiplatform - Convert arraylist to an immutable lsit

Question

I am trying to create a kotlin Multiplatform library which can later convert into java and javascript using IDEA 2019.3, kotlin 1.3

I have an array list with me and I want to convert it to a immutable list

val clean:List<String> = ArrayList<String>()

I could not see an option to convert clean to a immutable list. From here, I can see that kotlin has immutable list implementation but I could not see this in kotlin 1.3 multiplatform project.

Am I missing something obvious ? I could see a similar [old question][2] but according to this, it seems it should be available. Please help

score 1 · Answer 1 · answered Jan 07 '20 at 12:36

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Use Collections to converts an array list to Immutable list, Example:

Mutable Array list:

val clean:List<String> = ArrayList<String>()

Converts to Immutable list:

val immutableList = Collections.unmodifiableList(clean)

answered Jan 07 '20 at 12:36

Pawan Soni

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Collections is not available to be in the multiplatform kotlin project – nantitv Jan 07 '20 at 13:15
Please refer this link for multi platform sample projects https://kotlinlang.org/docs/reference/multiplatform.html – Pawan Soni Jan 07 '20 at 13:23

deHaar · Answer 2 · 2020-01-07T13:50:00.890

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In Kotlin, listOf(...) creates an immutable list, as stated in the documentation of the latest API.

That's why you can just write

val clean:List<String> = ArrayList<String>()
val immutableClean = listOf(clean.toImmutableList())

where immutableClean is a read only list.

edited Jan 07 '20 at 13:50

answered Jan 07 '20 at 12:46

deHaar

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Won't listOf( clean) produce a List>? In the end I tried something like listOf( *clean.toTypedArray()); – nantitv Jan 07 '20 at 13:15
@nantitv Yes, that's possible... I just payed attention to the return type being mutable or not ;-) – deHaar Jan 07 '20 at 13:24

kotlin1.3 multiplatform - Convert arraylist to an immutable lsit

2 Answers2